Method and apparatus for medical treatment utilizing long duration electromagnetic radiation

Abstract

A method and apparatus are provided for performing a medical procedure on a patient, for example a dermatological procedure, by use of electromagnetic radiation (EMR) having a relatively low peak power, and in particular a peak power low enough so as not to result in a phase change in the heater or chromophore absorbing radiation which would result in a significant reduction in its absorption, and of relatively long duration which is generally greater than, sometimes significantly greater than, the thermal relaxation time of the irradiated target.

1 . An apparatus for performing a dermatologic treatment on a target area of skin, comprising: 
 a source for generating optical electromagnetic radiation (EMR) having at least one wavelength being absorbable by a chromophore in the skin,    an applicator optically coupled to the source for applying the EMR to the target area, and    controls to cause the source to generate EMR having a duration in a range of about several seconds to about 20 seconds.    
   
   
       2 . Apparatus as claimed in  claim 1 , wherein the controls cause the source to generate EMR having a power, which is insufficient to cause a change in the chromophore that would result in significant loss of absorption of radiation by the chromophore.  
   
   
       3 . Apparatus as claimed in  claim 2 , wherein the controls operate the EMR to generate radiation with a substantially constant power over the duration.  
   
   
       4 . Apparatus as claimed in  claim 1 , wherein the controls operate the EMR to generate radiation with a power profile to provide a substantially constant temperature of the target area over the duration.  
   
   
       5 . Apparatus as claimed in  claim 2 , wherein the controls cause the EMR source to generate radiation with the peak power less than about 500 watts/cm 2 .  
   
   
       6 . Apparatus as claimed in  claim 1 , wherein the controls control an average power of radiation generated by the source such that the chromophore is heated to a temperature which is no more than approximately 110° C. so as to avoid vaporization of tissue.  
   
   
       7 . Apparatus as claimed in  claim 1 , wherein the source generates radiation suitable for causing hair removal and the chromophore is a hair shaft in a hair follicle, and wherein the controls cause the source to generate radiation for a duration long enough for sufficient heat from the hair shaft to reach an outer root sheath of the follicle to damage stem cells located thereat.  
   
   
       8 . Apparatus as claimed in  claim 1 , wherein the source generates radiation suitable for wrinkle removal and the chromophore is melanin at the DE junction, and wherein the controls cause the power profile and radiation duration to be sufficient to heat collagen in the papillary dermis sufficiently to restructure the collagen.  
   
   
       9 . Apparatus as claimed in  claim 1 , wherein the source generates radiation suitable for destruction of vascular lesions and the chromophore is blood in the vascular lesion, and wherein the controls cause the power and duration to be sufficiently longer than the thermal diffusion time of the lesion to coagulate walls of vessels.  
   
   
       10 . Apparatus as claimed in  claim 1 , further comprising a mechanism for cooling at least a portion of a skin surface over the target area at least substantially concurrently with application of EMR to the target area.  
   
   
       11 . Apparatus as claimed in  claim 1 , further comprising a detector for identifying at least one physiological condition of a subject whose skin is being treated, the controls being responsive to the detector for controlling at least one of the EMR power profile and duration.  
   
   
       12 . Apparatus as claimed in  claim 1 , wherein the radiation source is selected from the group consisting of a laser source and a non-coherent light source.  
   
   
       13 . Apparatus as claimed in  claim 1 , wherein the target area includes a highly absorbent heater portion and the source of electromagnetic radiation (EMR) generates at least one wavelength highly absorbed by the heater portion.  
   
   
       14 . Apparatus as claimed in  claim 1 , wherein the source of optical electromagnetic radiation (EMR) generates at least one wavelength in a range of about 0.4 microns to about 1.5 microns or in a range of about 0.95 microns to about 1.9 microns or in a range of about 2.1 microns to about 2.4 microns.  
   
   
       15 . Apparatus as claimed in  claim 2 , wherein the controls cause the EMR source to generate a fluence of about 50 Joules/cm 2 .  
   
   
       16 . Apparatus as claimed in  claim 2 , wherein the controls cause the EMR source to generate a fluence of about 150 Joules/cm 2 .  
   
   
       17 . Apparatus as claimed in  claim 4 , wherein said power profile exponentially decreases over said duration.